题解 | #合并表记录#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        while (scanner.hasNext()) {
            int nums = scanner.nextInt();
            TreeMap<Integer, Integer> map = new TreeMap<>();

            for (int i=0; i<nums; i++) {
                int key = scanner.nextInt();
                int value = scanner.nextInt();
                if (map.containsKey(key)) {
                    map.put(key, map.get(key)+value);
                } else {
                    map.put(key, value);
                }
            }

            for (Integer i : map.keySet()) {
                System.out.println(i + " " + map.get(i));
            }
        }
    }
}